ALK-Lung Analyte Control

The ALK gene is found on the short arm of chromosome 2. As an oncogene it was first identified as a translocation in anaplastic large cell lymphoma (ALCL) t(2;5)(p23;q35). In this instance the translocation caused a fusion product with the nucleophosmin gene: NPM-ALK. In reality the ALK translocation is a promiscuous event and associated with numerous fusions in multiple malignancies including EML4-ALK in non-small cell lung carcinoma (NSCLC).

The presence of ALK translocations can be determined by polymerase chain reaction (PCR) or FISH. ALK protein and fusion proteins can be detected by IHC. The most commonly used antibodies on the market, clones 5A4, D5F3^®, OTI1A4 and ALK1, all recognise C-terminus (see respective vendor data sheets). This is the conserved ALK region containing the tyrosine kinase domain. Therefore, all of these antibodies will recongise the wild type (WT) and should recognise the ALK fusion proteins.

In practice variation is often seen from laboratory to laboratory, this is due to a variety of reasons. These include, but not limited to; the efficacy of the antibody or its affinity for the target epitope, the relative availability of fusion protein, appropriate epitope retrieval and IHC protocols. This is readily evidenced in external quality assurance programs results. Our EML4-ALK control slides and blocks have been evaluated by a variety of assays but have been validated using the standardised assay available from Roche/Ventana.